"We believe that investors should take a breather during the expected strength of this quarter and the rapid rise in the stock," Piecyk wrote, citing potential changes in the wireless industry. "We expect post-paid wireless operators to remain firm in their plan to stunt the pace of phone upgrades in 2012 and we expect to see some initial evidence of their success in the current quarter."

Despite the downgrade on Monday, Apple continued to chug higher, with the company surpassing $600 billion in market cap for the first time on Tuesday. Shares touched a high of $644 that day, before settling at $628.44.

Apple shares have soared since the start of 2012, gaining 49.44%. That outpaces the 15.58% gain seen in the Nasdaq.

Apple also made headlines on Wednesday, but for very different reasons. The tech giant was named in a lawsuit from the Justice Department over e-book pricing.

The Justice Department sued Apple, along with book publishers Macmillan and Pearson's(PSO) Penguin Group "for conspiring to increase the prices that consumers pay for e-books," according to Attorney General Eric Holder.

French book publisher Hachette Book Group , News Corp.'s (NWSA) HarperCollins Publishers and Simon & Schuster , a division of CBS(CBS) , have already settled with the DOJ.

Price target raises for Apple were back in style Thursday, as Credit Suisse raised its target to $750 from $700, citing higher iPhone volumes.

"In a multi-device world, Apple is materially advantaged versus peers," said analyst Kulbinder Garcha in his research report. He raised his earnings estimates for 2012 and 2013 by 5% and 10%, respectively, to $50.14 a share and $60.72 a share.

Shares of Apple closed lower on the week, losing 4.49% to finish at $605.23.

Instagram, the popular photo-sharing app, reportedly has more than 40 million users, is the No. 1 free app on Apple's App Store, and recently became available on Google's Android market. The app lets users take pictures using their iOS and Android devices and apply filtered effects. These images can then be shared with friends and other Instagram users.